Rotary coin mechanisms are widely used in merchandise-dispensing machines such as bulk venders for dispensing gum balls and other small articles. Bulk venders are designed for self service by users with minimal maintenance, and as such are frequently placed in locations where their use cannot be readily supervised. As a result bulk venders are constantly subjected to attempts to steal merchandise, usually by children and adolescents.
One common type of theft from bulk venders involves the use of "slugs" approximating the size of the coin which the coin mechanism is designed to accept. This has led to the development of measuring devices with fairly precise tolerances, capable of determining the thickness and diameter of the inserted coin to within a few thousandths of an inch.
While in the past slugs were commonly cut or stamped out of sheet metal, more recently slugs composed of plastic or sturdy cardboard have also become popular due to their low cost and the ease with which such slugs can be produced to the required size. Cardboard slugs present a particular problem in bulk venders, because repeated attempts to force the mechanism to turn with an oversized cardboard slug in the coin recess can result in gradual wearing away of the edge of the slug until the edge has worn to a size within the tolerance of the measuring dog, at which point the mechanism will accept the slug.
A further problem is raised by the use of coins belonging to currency from other countries which may have a lower relative value than a coin of the intended denomination, but which coincidentally approximate the size and shape of the intended coin. In some cases such coins can be used in place of the intended coin, which similarly results in losses to bulk vender operators.
In some instances the coin intended to be accepted by the coin mechanism is magnetic. It is desirable in such cases to provide a system for preventing the mechanism from turning unless the deposited coin is magnetic, so that plastic or cardboard slugs, and non-magnetic coins from a foreign currency, will not be accepted by the coin mechanism even if they are of the correct size.
In other instances the coin intended to be accepted by the coin mechanism is not magnetic. It is desirable in such cases to provide a system for preventing the mechanism from turning unless the deposited coin is non-magnetic, so that steel slugs, magnetic tokens, and magnetic coins from a foreign currency will not be accepted by the coin mechanism even if they are of the correct size.
It is particularly desirable to provide a system which can be readily adapted for either of these situations using substantially the same components.